I am trying to find out information on the design of oil firing valves. The operation I volunteer at has one that has a very limited operating range. It was originally a slit port that was remade into a 1/2" round (hole straight through) valve (the original design would clog or jam from crud in the used crankcase oil we burn. The current design gives the fireman less than 10 degrees range of movement of the valve. I have some ideas on how I would do it, but I am looking to see what others have, with an eye towards having as much operating range as possible.Thanks in advance for any and all help.Michael SeitzMissoula MT

The problem is the decision to drill the round hole. You need to change to a triangle shaped hole, either by filling in the existing hole or making a new plug. The triangle shape will provide a smooth starting flow while providing a larger cavity at full open for dirt to pass.If the dirt clogged the old plug, what kept it from clogging the burner?

What he said about triangular or diamondular (?) shaped holes, and don't forget blowback - blowforward valves too. Might not hurt to put in a filter that can be shut off and dumped out without draining the tank as well. dave

The point is, you want an opening that increases slowly for the first 5 degrees of rotation, to give control, and then accelerates its shape change for the remainder of movement.The old slot was probably a constant rate valve, and worked fine, except as you discovered the slot clogged. I would rather see you fix the problem at the source, such as filtering your used oil at the collection point or at your storage tank.

While a filter on the old slot design might have been the ideal, that has been done away with through subsequent redesign. My thought was to have a variable depth groove cut into the rotating part of the valve body, with flow increasing as the valve was moved. This would also keep debris from fouling the valve, as the area beyond the inlet port would be larger. In this design the oil flow would be around the valve, rather than through it. It is hard to describe here and perhaps I should post a drawing somewhere. Does somebody has an idea on how to machine a triangular slot (short of drillings lots of holes and filing)? Thanks for the replies!Michael Seitz Missoula MT

Start with a round hole, and finish with the valve plug held between centers on a vertical rotary table bolted to the table of a milling machine, using progressively smaller end mills, until you just need to hand file the last bit of the points. If the outlet side of the valve is any shape larger than the inlet, but the inlet is well machined to graduate from tiny, it will be right.dave